1. Field of Invention
This invention, as used in a supercharger (an exhaust gas turbocharger) of internal combustion engines and so forth, relates to an adjustable nozzle mechanism for variable capacity turbines and its production method, and to a radial flow turbine configured to make an actuating gas flow from the spiral scroll formed in a turbine casing to the turbine rotor through the multiple nozzle vanes having wings of variable angle.
2. Description of the Related Art
In order to make a good match with regard to an internal combustion engine, between the outflow exhaust gas volume from the engine and the actuating gas flow volume which should be determined for the optimum operation condition of the supercharger, variable capacity superchargers, equipped with a variable capacity turbine capable of changing the exhaust gas volume to be sent from the spiral scroll to the turbine rotor in accordance with the operating condition of the engine, have been in widespread use in recent years.
A supercharger with such a variable capacity turbine is equipped with the adjustable nozzle mechanism in order to change the wing angle of the nozzle vane by rotating the nozzle vane with a link assembly so that it is capable of being driven for rotation around the turbine rotor shaft by the actuator through the actuator rod and the driving lever.
For a method of assembly and adjustment of such a variable nozzle mechanism, the invention of Japanese patent number 3,085,210 has been proposed.
In the concerned invention, a jig should be placed at the inner radius of the nozzle vane to perform setup for perfect closing of the nozzle vane and the link assembly to be driven for rotation around the turbine rotor shaft. The jig can be put in contact with the rear edge of the nozzle vane. The stopper pin is mounted after the nozzle vane and the lever plates are welded together upon putting the nozzle vane in contact with the jig in a state that the stopper pin, that is to be fitted into long slots provided at multiple positions along the circumferential direction of the link plate, is made non-functional or non-existing, and upon fitting the matching pin into the phase matching hole to finalize the entire link assembly in the perfect closing phase.
However, problems such as the following are concerns with the invention of Japanese patent number 3,085,210. Two different processes are required, one of which is to put the jig in contact with the nozzle vane in the nozzle vane-free state, wherein the stopper pin to be fitted into the long slots of the link plate is non-functional, and the other is to mount the stopper pin after welding the nozzle vane and the lever plate in the perfect closing phase of the entire link assembly with the matching pin fitted into the phase-matching hole. This in turn requires more assembling jigs, making the adjustable nozzle mechanism assembly and the related adjustment work troublesome, with additional man-hours resulting in a cost increase.
In addition, on the basis of the conventional art in which the structure becomes complex due to the link position determining pin included therein with the stopper pin fitted into the long slot at multiple positions in the circumferential direction of the link plate, the number of the part category and the number of parts themselves will therefore increase considerably. As a result, the device costs will increase accordingly.
Furthermore, as the setup of the total adjustable nozzle mechanism should be carried out by means of fitting the stopper pin into the long slot at multiple positions in the circumferential direction of the link plate and by means of making a match of the relative angle of the contact of the jig at the nozzle vane rear edge against the lever plate, the setup of the perfect closing may vary to cause a setup error. The perfect closing position of the adjustable nozzle mechanism must be determined primarily by the dimensional accuracy of the component parts, which may make it difficult to obtain the proper setup accuracy.
In consideration of the problems with the conventional art mentioned above, the object of this invention is to propose a method to realize assembly and adjustment, and the related assembly and adjustment facilities for the variable capacity turbine, requiring neither adjustment of the perfect closing position in the nozzle assembly nor the jigs for assembly and adjustment thereof, by which the adjustment work can be simplified to decrease man-hours, as well as assembly and adjustment costs. The structure can also be simplified to decrease part category numbers and the number of parts itself, thus decreasing part costs and furthermore enabling the nozzle vane setup of the adjustable nozzle mechanism to a comparatively high degree of accuracy without being influenced by the degree of dimensional accuracy of the component parts, such as the nozzle vane and the link assembly.
In order to solve the concerned problems, the variable capacity turbine for applying this invention comprises a number of nozzle vanes, which are arranged along the circumference of the turbine and provided on nozzle shafts which are supported on a turbine casing in such a way that the nozzle vanes can rotate, and which vary the vane angle. A nozzle driving member drives the nozzle vanes, and is enabled to rotate around the turbine shaft by an actuator. A turbine rotor is set free for rotation on an inner radial side of the nozzle vanes. The variable capacity turbine is driven for rotation of the turbine rotor by conducting the actuating gas from the scroll in the turbine casing in the inner radial direction through the nozzle vanes to the turbine rotor.
In the event of manufacturing the adjustable nozzle mechanism used in such variable capacity turbine, it is distinguished by a manufacturing method according to this invention, which comprises providing a plurality of joint members (lever plates) which are the same in number as the nozzle shafts, and connecting the plurality of nozzle vanes and the nozzle driving member (link plate), fitting and fixing each nozzle shaft to one end of each lever plate after setting a predetermined positional relationship between the wing angle of the nozzle vanes and the fitting direction of the fixing section of the lever plate; and engaging another end of each lever plate with the nozzle driving member (link plate).
For the concrete fixing method of the nozzle shaft to joint member (lever plate), the method comprises forming a coupling hole in each joint member (lever plate), then forming a flat or curved surface on one sidewall of each coupling hole. A coupling shaft is provided with a fitting surface on the end of the nozzle shaft for nozzle vane, the fitting surface corresponding to the shape of the coupling hole of the joint member (lever plate) for creating a stopper. The coupling shaft is filled into the coupling hole without causing plastic deformation at the coupling shaft or coupling hole, and a stopper surface of the shaft is engaged with a stopper surface on the coupling hole so that the joint member (lever plate) and the nozzle shaft cannot rotate relatively because of the stopper. Finally, processing for anti-decoupling is carried out to prevent the nozzle shaft from squeezing out of the side surface of the joint members by using the chamfered portion having a larger diameter (chamfered portion) at the edge portion of the nozzle shaft.
The anti-decoupling is preferably done by punching the shaft edge of the coupling shaft by using the chamfered portion at the edge after engaging the coupling hole of the joint member with the coupling shaft of the nozzle shaft. The anti-decoupling process at the edge can be substituted by light welding or the like.
This invention further features that the concrete engaging method of the joint members (lever plate) with the nozzle driving member (link plate) is to fit the slots with the fitting pins equal in number to the joint members. The fitting pins protrude along the circumferential direction on the nozzle driving member. The slots are opened in a nearly radial direction on the other edge of each of the joint members to engage with the fitting pins of the nozzle driving member.
The variable capacity turbine for applying this invention comprises a number of nozzle vanes which are arranged along the circumference of the turbine and provided on nozzle shafts which are supported on the turbine casing in such a way that the nozzle vanes can rotate to vary the vane angle. A nozzle driving member drives the nozzle vanes, and is enabled to rotate around the turbine shaft by the actuator. A turbine rotor is set free for rotation on an inner radial side of the nozzle vanes. The variable capacity turbine is driven for rotation of the turbine rotor by conducting the actuating gas from the scroll in the turbine casing in thinner radial direction through the nozzle vanes to the turbine rotor.
The adjustable nozzle mechanism used in such variable capacity turbine is distinguished by a configuration, comprising a plurality of lever plates which are provided between the nozzle mount and the link plate, one end of each lever plate is fitted and fixed to a respective nozzle shaft after setting a predetermined positional relationship between the wing angle of the nozzle vanes and the fitting direction of the fixing section of the lever plate. The lever plate is provided with a slot which is open in a nearly radial direction on the other edge. The same number of fitting pins protrude from along the circumferential direction and toward the lever plate side on the nozzle driving member, the fitting pins being engaged with the slots of the lever plates.
In accordance with this invention, adjustment of the adjustable nozzle mechanism, that is, the position setup of the wing angle of the nozzle vane and the nozzle driving member, can be made with such an extremely simple process. In this process, the coupling hole provided at one edge of the lever plate and the coupling shaft at the end of the nozzle shaft are fitted after being set up geometrically so that the wing angle and the rotating angle of the link plate composing the nozzle driving member may be in the predetermined relation. The edge of the nozzle shaft is the n punched into one of the chamfered portion of the edge portion in order to be fixed on the lever plate. Then the lever plate and the link plate can be engaged to each other by engaging the pins with the slots provided at the end of the lever plate.
With these simplified processes, adjustment of the adjustable nozzle mechanism during the nozzle assembly procedure is no longer required and therefore the assembly man-hours are decreased, particular assembly facilities such as jigs are not needed, and as a result, assembly costs are decreased. The jigs are still required with the invention of the Japanese patent number 3,085,210 in such a way that the adjustment should be made for the perfect closing position during nozzle assembly procedure by using multiple long slots of the link plate, stopper pin and jigs.
Furthermore, as the adjustable nozzle mechanism according to this invention is configured in a manner that the one edge side of the joint members (lever plate) and the nozzle shaft are fixed upon the set geometrical relations between them and the nozzle driving member (link plate) is joined to the other edge side of each joint member, the structure is simplified as compared with the conventional art, and the number of part categories and parts itself are considerably decreased. Part costs are decreased accordingly.
Furthermore, with this invention, configured such that the nozzle driving member is joined to the other edge of each joint member after the se have been fitted, on the condition that the wing angle of the nozzle vane and the rotating angle of the nozzle driving member (link plate) had been set previously in the geometrical relation as required, and that adjustment of the adjustable nozzle mechanism, that is, the position setup of the wing angle of the nozzle vane and the nozzle driving member is available neither with a setting error that would arise in the conventional art from the variable setup for the perfect closing caused by the adjustment for the perfect closing position during the nozzle assembling procedure using the multiple long slots, the stopper pin and jig, nor the perfect closing position of the adjustable nozzle mechanism should be determined primarily by the component parts, the setup herein of the adjustable nozzle mechanism is available to a high degree of accuracy without fear of influence by the dimensional accuracy of the nozzle assembly and the link assembly, as well as the enabling of the various requirement settings of the adjustable nozzle mechanism.
Still furthermore, with this invention, configured such that the lever plates, equal in number to the nozzle vanes, are placed between the nozzle mount and the link plate in the turbine shaft axis, that the one edge of the lever plate is fixed on the nozzle shaft of the nozzle vane, that the fitting pin protruding toward the lever plate side in the link plate is fitted into the slots on the other edge of the lever plate, that the stopper between the lever plate and the edge of the nozzle shaft is processed with the use of the chamfered portion in order to prevent the stopper portion from squeezing out of the side face of the lever plate, it becomes possible to assemble the link plate and lever plate with a minimum distance. Therefore, the distance between the link plate and the nozzle mount over the lever plate sandwiched thereby becomes shorter, and the length in the shaft axis direction of the adjustable nozzle mechanism is, as a result, shortened.
Still furthermore, the punched portion avoids protrusion from the link plate side, and erroneous operation of the adjustable nozzle mechanism by the friction and interference between the link plate and the punched portion is also avoided.